Chemical vapor deposition (CVD) is commonly used for forming thin layers of material known as films over an integrated circuit substrate and other surfaces. The substrate commonly known as a wafer is heated in a reaction chamber, and is exposed to material gases introduced into the chamber. As a result of thermal decomposition and/or reaction of the material gases, a film such as a gallium arsenide compound is formed on the surface of the wafer.
In a system for such a CVD process, as a result of contact with the material gas, unnecessary byproducts such as arsenide tend to be deposited on various surfaces such as the wall surfaces provided opposite to the susceptors for the wafer to be processed for controlling the flow of the material gas. In particular, heater units for heating the wafers to be processed tend to be heavily contaminated by such material deposition which is known to be detrimental to satisfactory operation of the heater units.